Hot-press deep-drawing forming method and hot-press deep-drawing forming method apparatus

Abstract

A hot-press deep-drawing forming apparatus includes a punch that constitutes a lower die and a die that constitutes an upper die. The punch has an inner-face forming surface that forms the inner face of a product, and a bent corner against which a scrap section S of a workpiece W abuts. The die has an outer-face forming surface that forms the outer surface of the product. A blank holder and a pre-forming die that clamp the scrap section are caused to move, together with the die, until the clamped scrap section abuts the bent corner. The movement of the blank holder and the pre-forming die is stopped after the scrap section has abutted the bent corner.

The invention claimed is: 
     
       1. A hot-press deep-drawing forming method of forming a product that has a main body of U-shaped cross-sectional shape provided with a front wall and a side wall, and a flange that is contiguous with the main body, through press-working of a workpiece made of a steel plate and heated at or above a transformation temperature, the method comprising:
 a pre-forming die movement step of causing a die, having a built-in cooling mechanism and provided with an outer-face forming surface that forms an outer surface of the product, as well as a blank holder and a pre-forming die that clamp a scrap section of the workpiece, to relatively perform an approach movement towards a punch, having a built-in cooling mechanism and provided with an inner-face forming surface that forms an inner face of the product, and with a bent corner against which the scrap section abuts, the approach movement being performed until the scrap section contacts with the bent corner; and 
 a final forming step of stopping the movement of the scrap section that is clamped by the blank holder and the pre-forming die, while the die moves towards the punch after the scrap section has contacted with the bent corner. 
 
     
     
       2. The hot-press deep-drawing forming method according to  claim 1 , wherein the punch is a lower die, the die is an upper die that is vertically movable towards the punch, the pre-forming die is mounted on the upper die via an elastic member, the blank holder is mounted on the lower die by a holder driving member, and while the die moves towards the punch after the scrap section has contacted with the bent corner, the elastic member is caused to contract and the movement of the pre-forming die is stopped. 
     
     
       3. The hot-press deep-drawing forming method according to  claim 1 , wherein the punch is a lower die, the die is an upper die that is vertically movable towards the punch, the pre-forming die is mounted on a slide die that is mounted on the die so as to be vertically movable, the blank holder is mounted on the punch by a holder driving member, and while the die moves towards the punch after the scrap section has contacted with the bent corner, the movement of the pre-forming die is stopped by the slide die. 
     
     
       4. The method of  claim 1  wherein the bent corner is an arcuate bent corner in cross-section. 
     
     
       5. The method of  claim 1  further comprising separation of the scrap section from a remainder of the workpiece following completion of the die moving towards the punch after the scrap section has contacted with the bent corner. 
     
     
       6. The method of  claim 5  wherein the separation is carried out by a cutting operation. 
     
     
       7. The method of  claim 1  wherein there is avoided heat dissipation at the scrap section by having a spacing gap formed between exterior siding of the die and punch combination and interior siding of the pre-forming die and the blank holder in a region where the scrap section bridges the spacing gap. 
     
     
       8. The method of  claim 1  wherein the forming includes having the scrap section extend so as to be sandwiched between the die and the punch combination. 
     
     
       9. The method of  claim 1  further comprising applying a heat removal treatment to a product section of the work piece with the punch and the die without applying a heat removal treatment to the scrap section. 
     
     
       10. A hot-press deep-drawing forming apparatus for forming a product that has a main body of U-shaped cross-sectional shape provided with a front wall and a side wall, and a flange that is contiguous with the main body, through press-working of a workpiece made of a steel plate and heated at or above a transformation temperature, the apparatus comprising:
 a punch, having a built-in cooling mechanism and provided with an inner-face forming surface that forms an inner face of the product, and with a bent corner against which a scrap section of the workpiece abuts; 
 a die, having a built-in cooling mechanism, provided with an outer-face forming surface that forms an outer surface of the product, and performing an approach-separation movement relatively to the punch; 
 a blank holder against which the scrap section abuts; 
 a pre-forming die that clamps the scrap section together with the blank holder; and 
 a double action mechanism that causes the blank holder and the pre-forming die to move, together with the die, until the scrap section clamped by the blank holder and the pre-forming die contacts with the bent corner, and that stops the movement of the blank holder and of the pre-forming die while the die approaches the punch after the scrap section has contacted with the bent corner. 
 
     
     
       11. The hot-press deep-drawing forming apparatus according to  claim 10 , wherein the punch forms a lower die, the die forms an upper die that is vertically movable towards the lower die, the pre-forming die is mounted on the upper die via an elastic member, the blank holder is mounted on the lower die by a holder driving member, and while the die moves towards the punch after the scrap section has contacted with the bent corner, the elastic member is caused to contract and the movement of the pre-forming die is stopped. 
     
     
       12. The hot-press deep-drawing forming apparatus according to  claim 10 , wherein the punch forms a lower die, the die forms an upper die that is vertically movable towards the punch, the pre-forming die is mounted on a slide die that is mounted on the die so as to be vertically movable, the blank holder is mounted on the punch by a holder driving member, and while the die moves towards the punch after the scrap section has contacted with the bent corner, the movement of the pre-forming die is stopped by the slide die. 
     
     
       13. The apparatus of  claim 10  wherein bent corner is an arcuate bent corner in cross-section. 
     
     
       14. The apparatus of  claim 10  wherein there is a spacing gap formed between exterior siding of the die and punch combination and interior siding of the pre-forming die and the blank holder in a region where the scrap section bridges the spacing gap. 
     
     
       15. The apparatus of  claim 10  wherein the die and punch are configured such that the scrap section extends so as to be sandwiched between the die and the punch combination. 
     
     
       16. The apparatus of  claim 10  wherein the apparatus is configured as to enable a heat removal treatment to a product section of the workpiece with the punch and the die without applying a heat removal treatment to the scrap section.